Arrangement for and method of projecting an image with pixel mapping

ABSTRACT

A laser beam is swept by a scan mirror as a pattern of scan lines on a projection surface. The scan mirror moves at a variable speed along each scan line. Each scan line has a number of pixels. The pixels have time durations proportional to the variable speed of the scan mirror. A profile memory stores the time durations of the pixels. A controller causes selected pixels arranged along each scan line to be illuminated for the time durations stored by the profile memory to produce an image of uniform brightness and of uniformly sized pixels and in color.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to projecting a two-dimensionalimage of high quality especially in color.

2. Description of the Related Art

It is generally known to project a two-dimensional image on a projectionsurface based on a pair of scan mirrors which oscillate in mutuallyorthogonal directions to scan a laser beam over a raster patterncomprised of a plurality of scan lines. The image is created in theraster pattern by energizing or pulsing a laser on and off at selectedtimes, thereby illuminating selected pixels with a beam spot and notilluminating other pixels in each scan line. The number of distinct beamspots or pixels that can fit in each scan line is known as theresolution.

One of the scan mirrors, sometimes referred to herein as an X-mirror,sweeps the laser beam at a relatively faster speed generally along ascan direction extending along the horizontal, and the other of the scanmirrors, sometimes referred to herein as a Y-mirror, sweeps the scanline at a relatively slower speed generally perpendicular to the scandirection extending along the vertical. The X-mirror is oscillated,typically at resonance, at a scan frequency and at a speed that variesalong each scan line. Thus, the X-mirror has a maximum speed at thecenter of each scan line and a minimum speed at the ends of each scanline.

The variable speed of the X-mirror causes the pixels to have variabletime durations in order to obtain pixels of the same size on theprojection surface. The variable speed of the X-mirror also causes thepixels to have a variable brightness, that is, the projected imageappears brighter at those pixels where the X-mirror has a slower speed.These variable time durations and the variable brightness must be takeninto account in order to project the image with uniformly sized pixelsand uniform brightness.

SUMMARY OF THE INVENTION OBJECTS OF THE INVENTION

Accordingly, it is a general object of this invention to provide animage projection arrangement that projects a two-dimensional image,especially in color, with uniformly sized pixels and uniform brightnessin accordance with the method of this invention.

An additional object is to provide a miniature, compact, lightweight,and portable color image projection module useful in many instruments ofdifferent form factors.

FEATURES OF THE INVENTION

In keeping with these objects and others, which will become apparenthereinafter, one feature of this invention resides, briefly stated, inan image projection arrangement for, and a method of, projecting atwo-dimensional image of high quality, especially in color. Thearrangement includes a laser assembly for generating a laser beam; ascanner for sweeping the laser beam as a pattern of scan lines on aprojection surface at a distance from the laser assembly, each scan linehaving a number of pixels; and a controller operatively connected to thelaser assembly and the scanner, for causing selected pixels to beilluminated, and rendered visible, by the laser beam to produce theimage.

In accordance with one aspect of this invention, the scanner includes ascan mirror, i.e., the X-mirror, movable at a speed that varies alongeach scan line. The pixels have respective time durations proportionalto the variable speed of the X-mirror in order to obtain pixels of thesame size on the projection surface. Hence, to take such variable timedurations into account, a profile memory is provided for storing thetime durations of the pixels. The controller is operatively connected tothe profile memory to cause the selected pixels to be illuminated forthe time durations stored in the profile memory.

The time durations can be stored only for a single representative scanline, for example, the center scan line, in which case, the stored timedurations for the representative scan line are applied to all of theother scan lines; however, this leads to errors particularly at theupper and lower regions of the raster scan which are furthest from thecenter scan line. Alternatively, the time durations can be stored forall of the scan lines; however, this requires a multitude of storagelocations for the profile memory. Preferably, to minimize the memorystorage requirement, the time durations are stored for a single scanline, such as the center scan line, and then only the differences withthe adjacent scan lines are stored in succession for all the scan lines.

As discussed above, the brightness of the image varies with the timedurations, that is, the projected image appears brighter at those pixelswhere the X-mirror has a slower speed. In further accordance with thisinvention, the stored time durations are inverted (the brightness isinversely related to the time durations), and the controller generates abrightness compensation signal. This signal is then multiplied with theincoming video data to ensure that each pixel has the same brightness.

In the preferred embodiment, the laser assembly includes a plurality oflasers for respectively generating a plurality of laser beams ofdifferent wavelengths, for example, red, blue and green laser beams, andan optical assembly for focusing and nearly collinearly arranging thelaser beams to form the laser beam as a composite beam which is directedto the scan mirror. The scan mirror is operative for sweeping thecomposite beam along a first direction at a first scan rate and over afirst scan angle. Another oscillatable scan mirror is operative forsweeping the composite beam along a second direction substantiallyperpendicular to the first direction, and at a second scan ratedifferent from the first scan rate, and at a second scan angle differentfrom the first scan angle. At least one of the scan mirrors isoscillated by an inertial drive.

The controller includes means for energizing the lasers to illuminatethe selected pixels for the time durations stored in the profile memory,and for deenergizing the lasers to non-illuminate pixels other than theselected pixels. The controller also includes means for effectivelyaligning the laser beams collinearly by delaying turning on and off thepixels of each of the laser beams relative to each other.

The support, lasers, scan mirrors, controller and optical assemblypreferably occupy a volume of about seventy cubic centimeters, therebyconstituting a compact module, which is interchangeably mountable inhousings of different form factors, including, but not limited to, apen-shaped, gun-shaped or flashlight-shaped instrument, a personaldigital assistant, a pendant, a watch, a computer, and, in short, anyshape due to its compact and miniature size. The projected image can beused for advertising or signage purposes, or for a television orcomputer monitor screen, and, in short, for any purpose desiringsomething to be displayed.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a hand-held instrument projecting animage at a working distance therefrom;

FIG. 2 is an enlarged, overhead, perspective view of an image projectionarrangement in accordance with this invention for installation in theinstrument of FIG. 1;

FIG. 3 is a top plan view of the arrangement of FIG. 2;

FIG. 4 is a perspective front view of an inertial drive for use in thearrangement of FIG. 2;

FIG. 5 is a perspective rear view of the inertial drive of FIG. 4;

FIG. 6 is a perspective view of a practical implementation of thearrangement of FIG. 2;

FIG. 7 is an electrical schematic block diagram depicting operation ofthe arrangement of FIG. 2; and

FIG. 8 is a schematic block diagram of a pixel mapping circuit used bythe arrangement of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference numeral 10 in FIG. 1 generally identifies a hand-heldinstrument, for example, a personal digital assistant, in which alightweight, compact, image projection arrangement 20, as shown in FIG.2, is mounted and operative for projecting a two-dimensional color imageon a projection surface at a variable distance from the instrument. Byway of example, an image 18 is situated within a viewing range ofdistances relative to the instrument 10.

As shown in FIG. 1, the image 18 extends over an optical horizontal scanangle A extending along the horizontal direction, and over an opticalvertical scan angle B extending along the vertical direction, of theimage. As described below, the image is comprised of illuminated andnon-illuminated pixels on a raster pattern of scan lines swept by ascanner in the arrangement 20.

The parallelepiped shape of the instrument 10 represents just one formfactor of a housing in which the arrangement 20 may be implemented. Theinstrument can be shaped with many different form factors, such as apen, a cellular telephone, a clamshell or a wristwatch.

In the preferred embodiment, the arrangement 20 measures about seventycubic centimeters in volume. This compact, miniature size allows thearrangement 20 to be mounted in housings of many diverse shapes, largeor small, portable or stationary, including some having an on-boarddisplay 12, a keypad 14, and a window 16 through which the image isprojected.

Referring to FIGS. 2 and 3, the arrangement 20 includes a solid-state,preferably a semiconductor laser 22 which, when energized, emits abright red laser beam at about 635-655 nanometers. Lens 24 is abi-aspheric convex lens having a positive focal length and is operativefor collecting virtually all the energy in the red beam and forproducing a diffraction-limited beam. Lens 26 is a concave lens having anegative focal length. Lenses 24, 26 are held by non-illustratedrespective lens holders apart on a support (not illustrated in FIG. 2for clarity) inside the instrument 10. The lenses 24, 26 shape the redbeam profile over the working distance.

Another solid-state, semiconductor laser 28 is mounted on the supportand, when energized, emits a diffraction-limited blue laser beam atabout 440 nanometers. Another bi-aspheric convex lens 30 and a concavelens 32 are employed to shape the blue beam profile in a manneranalogous to lenses 24, 26.

A green laser beam having a wavelength on the order of 532 nanometers isgenerated not by a semiconductor laser, but instead by a green module 34having an infrared diode-pumped, Nd-doped, YAG crystal laser whoseoutput beam at 1064 nanometers. A non-linear frequency doubling crystalis included in the infrared laser cavity between two laser mirrors.Since the infrared laser power inside the cavity is much larger than thepower coupled outside the cavity, the frequency doubler is moreefficient in generating the double frequency green light inside thecavity. The output mirror of the laser is reflective to the 1064 nminfrared radiation, and transmissive to the doubled 532 nm green laserbeam. Since the correct operation of the solid-state laser and frequencydoubler require precise temperature control, a semiconductor devicerelying on the Peltier effect is used to control the temperature of thegreen laser module. The thermoelectric cooler can either heat or coolthe device depending on the polarity of the applied current. Athermistor is part of the green laser module in order to monitor itstemperature. The readout from the thermistor is fed to a controller,which adjusts the control current to the thermoelectric cooleraccordingly.

As explained below, the lasers are pulsed in operation at frequencies onthe order of 100 MHz. The red and blue semiconductor lasers 22, 28 canbe pulsed directly via the applied drive currents at such highfrequencies, but the currently available green solid-state laserscannot. As a result, the green laser beam exiting the green module 34 ispulsed with an acousto-optical modulator (AOM) 36 that creates anacoustic traveling wave inside a crystal for diffracting the green beam.The AOM 36, however, produces a zero-order, non-diffracted beam 38 and afirst-order, pulsed, diffracted beam 40. The beams 38, 40 diverge fromeach other and, in order to separate them to eliminate the undesirablezero-order beam 38, the beams 38, 40 are routed along a long, foldedpath having a folding mirror 42. Alternatively, the AOM can be usedinternally to the green laser module to pulse the green laser beam.Other possible ways to modulate the green laser beam includeelectro-absorption modulation, or a Mach-Zender interferometer. Thebeams 38, 40 are routed through positive and negative lenses 44, 46.However, only the diffracted green beam 40 is allowed to impinge upon,and reflect from, the folding mirror 48. The non-diffracted beam 38 maybe absorbed by an absorber 50, preferably mounted on the mirror 48, orcan be used for another useful function.

The arrangement includes a pair of dichroic filters 52, 54 arranged tomake the green, blue and red beams as collinear as possible beforereaching a scanning assembly 60. Filter 52 allows the green beam 40 topass therethrough, but the blue beam 56 from the blue laser 28 isreflected by the interference effect. Filter 54 allows the green andblue beams 40, 56 to pass therethrough, but the red beam 58 from the redlaser 22 is reflected by the interference effect.

The nearly collinear beams 40, 56, 58 are directed to, and reflectedoff, a stationary fold mirror 62. The scanning assembly 60 includes afirst scan mirror 64 oscillatable by an inertial drive 66 (shown inisolation in FIGS. 4-5) at a first scan rate to sweep the laser beamsreflected off the fold mirror 62 over the first horizontal scan angle A,and a second scan mirror 68 oscillatable by an electromagnetic drive 70at a second scan rate to sweep the laser beams reflected off the firstscan mirror 64 over the second vertical scan angle B. In a variantconstruction, the scan mirrors 64, 68 can be replaced by a singletwo-axis mirror.

The inertial drive 66 is a high-speed, low electrical power-consumingcomponent. Details of the inertial drive can be found in U.S. patentapplication Ser. No. 10/387,878, filed Mar. 13, 2003, assigned to thesame assignee as the instant application, and incorporated herein byreference thereto. The use of the inertial drive reduces powerconsumption of the scanning assembly 60 to less than one watt and, inthe case of projecting a color image, as described below, to less thanten watts.

The drive 66 includes a movable frame 74 for supporting the scan mirror64 by means of a hinge that includes a pair of collinear hinge portions76, 78 extending along a hinge axis and connected between oppositeregions of the scan mirror 64 and opposite regions of the frame. Theframe 74 need not surround the scan mirror 64, as shown.

The frame, hinge portions and scan mirror are fabricated of an integral,generally planar, silicon substrate, which is approximately 150 micronsthick. The silicon is etched to form omega-shaped slots having upperparallel slot sections, lower parallel slot sections, and U-shapedcentral slot sections. The scan mirror 64 preferably has an oval shapeand is free to move in the slot sections. In the preferred embodiment,the dimensions along the axes of the oval-shaped scan mirror measure 749microns×1600 microns. Each hinge portion measures 27 microns in widthand 1130 microns in length. The frame has a rectangular shape measuring3100 microns in width and 4600 microns in length.

The inertial drive is mounted on a generally planar, printed circuitboard 80 and is operative for directly moving the frame and, by inertia,for indirectly oscillating the scan mirror 64 about the hinge axis. Oneembodiment of the inertial drive includes a pair of piezoelectrictransducers 82, 84 extending perpendicularly of the board 80 and intocontact with spaced apart portions of the frame 74 at either side ofhinge portion 76. An adhesive may be used to insure a permanent contactbetween one end of each transducer and each frame portion. The oppositeend of each transducer projects out of the rear of the board 80 and iselectrically connected by wires 86, 88 to a periodic alternating voltagesource (not shown).

In use, the periodic signal applies a periodic drive voltage to eachtransducer and causes the respective transducer to alternatingly extendand contract in length. When transducer 82 extends, transducer 84contracts, and vice versa, thereby simultaneously pushing and pullingthe spaced apart frame portions and causing the frame to twist about thehinge axis. The drive voltage has a frequency corresponding to theresonant frequency of the scan mirror. The scan mirror is moved from itsinitial rest position until it also oscillates about the hinge axis atthe resonant frequency. In a preferred embodiment, the frame and thescan mirror are about 150 microns thick, and the scan mirror has a highQ factor. A movement on the order of 1 micron by each transducer cancause oscillation of the scan mirror at scan angles in excess of 15degrees.

Another pair of piezoelectric transducers 90, 92 extends perpendicularlyof the board 80 and into permanent contact with spaced apart portions ofthe frame 74 at either side of hinge portion 78. Transducers 90, 92serve as feedback devices to monitor the oscillating movement of theframe and to generate and conduct electrical feedback signals alongwires 94, 96 to a feedback control circuit (not shown).

Although light can reflect off an outer surface of the scan mirror, itis desirable to coat the surface of the mirror 64 with a specularcoating made of gold, silver, aluminum, or a specially designed highlyreflective dielectric coating.

The electromagnetic drive 70 includes a permanent magnet jointly mountedon and behind the second scan mirror 68, and an electromagnetic coil 72operative for generating a periodic magnetic field in response toreceiving a periodic drive signal. The coil 72 is adjacent the magnet sothat the periodic field magnetically interacts with the permanent fieldof the magnet and causes the magnet and, in turn, the second scan mirror68 to oscillate.

The inertial drive 66 oscillates the scan mirror 64 at a high speed at ascan rate preferably greater than 5 kHz and, more particularly, on theorder of 18 kHz or more. This high scan rate is at an inaudiblefrequency, thereby minimizing noise and vibration. The electromagneticdrive 70 oscillates the scan mirror 68 at a slower scan rate on theorder of 40 Hz which is fast enough to allow the image to persist on ahuman eye retina without excessive flicker.

The faster mirror 64 sweeps a generally horizontal scan line, and theslower mirror 68 sweeps the generally horizontal scan line vertically,thereby creating a raster pattern which is a grid or sequence of roughlyparallel scan lines from which the image is constructed. Each scan linehas a number of pixels. The image resolution is preferably XGA qualityof 1024×768 pixels. Over a limited working range, a high-definitiontelevision standard, denoted 720 p, 1270×720 pixels, can be obtained. Insome applications, a one-half VGA quality of 320×480 pixels, orone-fourth VGA quality of 320×240 pixels, is sufficient. At minimum, aresolution of 160×160 pixels is desired.

The roles of the mirrors 64, 68 could be reversed so that mirror 68 isthe faster, and mirror 64 is the slower. Mirror 64 can also be designedto sweep the vertical scan line, in which event, mirror 68 would sweepthe horizontal scan line. Also, the inertial drive can be used to drivethe mirror 68. Indeed, either mirror can be driven by anelectromechanical, electrical, mechanical, electrostatic, magnetic, orelectromagnetic drive.

The slow-mirror is operated in a constant velocity sweep-mode duringwhich time the image is displayed. During the mirror's return, themirror is swept back into the initial position at its natural frequency,which is significantly higher. During the mirror's return trip, thelasers can be powered down in order to reduce the power consumption ofthe device.

FIG. 6 is a practical implementation of the arrangement 20 in the sameperspective as that of FIG. 2. The aforementioned components are mountedon a support, which includes a top cover 100 and a support plate 102.Holders 104, 106, 108, 110, 112 respectively hold folding mirrors 42,48, filters 52, 54 and fold mirror 62 in mutual alignment. Each holderhas a plurality of positioning slots for receiving positioning postsstationarily mounted on the support. Thus, the mirrors and filters arecorrectly positioned. As shown, there are three posts, therebypermitting two angular adjustments and one lateral adjustment. Eachholder can be glued in its final position.

The image is constructed by selective illumination of the pixels in oneor more of the scan lines. As described below in greater detail withreference to FIG. 7, a controller 114 causes selected pixels in theraster pattern to be illuminated, and rendered visible, by the threelaser beams. For example, red, blue and green power controllers 116,118, 120 respectively conduct electrical currents to the red, blue andgreen lasers 22, 28, 34 to energize the latter to emit respective lightbeams at each selected pixel, and do not conduct electrical currents tothe red, blue and green lasers to deenergize the latter tonon-illuminate the other non-selected pixels. The resulting pattern ofilluminated and non-illuminated pixels comprises the image, which can beany display of human- or machine-readable information or graphic.

Referring to FIG. 1, the raster pattern is shown in an enlarged view.Starting at an end point, the laser beams are swept by the inertialdrive along the generally horizontal direction at the horizontal scanrate to an opposite end point to form a scan line. Thereupon, the laserbeams are swept by the electromagnetic drive 70 along the verticaldirection at the vertical scan rate to another end point to form asecond scan line. The formation of successive scan lines proceeds in thesame manner.

The image is created in the raster pattern by energizing or pulsing thelasers on and off at selected times under control of the microprocessor114 or control circuit by operation of the power controllers 116, 118,120. The lasers produce visible light and are turned on only when apixel in the desired image is desired to be seen. The color of eachpixel is determined by one or more of the colors of the beams. Any colorin the visible light spectrum can be formed by the selectivesuperimposition of one or more of the red, blue, and green lasers. Theraster pattern is a grid made of multiple pixels on each line, and ofmultiple lines. The image is a bit-map of selected pixels. Every letteror number, any graphical design or logo, and even machine-readable barcode symbols, can be formed as a bit-mapped image.

As shown in FIG. 7, an incoming video signal having vertical andhorizontal synchronization data, as well as pixel and clock data, issent to red, blue and green buffers 122, 124, 126 under control of themicroprocessor 114. The storage of one full VGA frame requires manykilobytes, and it would be desirable to have enough memory in thebuffers for two full frames to enable one frame to be written, whileanother frame is being processed and projected. The buffered data issent to a formatter 128 under control of a speed profiler 130 and tored, blue and green look up tables (LUTs) 132, 134, 136 to correctinherent internal distortions caused by scanning, as well as geometricaldistortions caused by the angle of the display of the projected image.The resulting red, blue and green digital signals are converted to red,blue and green analog signals by digital to analog converters (DACs)138, 140, 142. The red and blue analog signals are fed to red and bluelaser drivers (LDs) 144, 146 which are also connected to the red andblue power controllers 116, 118. The green analog signal is fed to anacousto-optical module (AOM) radio frequency (RF) driver 150 and, inturn, to the green laser 34 which is also connected to a green LD 148and to the green power controller 120.

Feedback controls are also shown in FIG. 7, including red, blue andgreen photodiode amplifiers 152, 154, 156 connected to red, blue andgreen analog-to-digital (A/D) converters 158, 160, 162 and, in turn, tothe microprocessor 114. Heat is monitored by a thermistor amplifier 164connected to an A/D converter 166 and, in turn, to the microprocessor.

The scan mirrors 64, 68 are driven by drivers 168, 170 which are fedanalog drive signals from DACs 172, 174 which are, in turn, connected tothe microprocessor. Feedback amplifiers 176, 178 detect the position ofthe scan mirrors 64, 68, and are connected to feedback A/Ds 180, 182and, in turn, to the microprocessor.

A power management circuit 184 is operative to minimize power whileallowing fast on-times, preferably by keeping the green laser on all thetime, and by keeping the current of the red and blue lasers just belowthe lasing threshold.

A laser safety shut down circuit 186 is operative to shut the lasers offif either of the scan mirrors 64, 68 is detected as being outside ofrated values.

It will be recalled that the inertial drive 66 oscillates the scanmirror 64 at a resonant frequency whose speed varies along each scanline. The scan mirror 64 has a maximum speed at the center of each scanline and a minimum speed at the ends of each scan line. The variablespeed of the scan mirror 64 causes the pixels to have variable timedurations in order to obtain pixels of the same size on the projectionsurface. The variable speed of the scan mirror 64 also causes the pixelsto have a variable brightness, that is, the projected image appearsbrighter at those pixels where the scan mirror 64 has a slower speed.These variable time durations and the variable brightness are taken intoaccount by a pixel mapping circuit depicted in FIG. 8 in order toproject the image with uniformly sized pixels and uniform brightness.

As shown in FIG. 8, a clock 200 counts “tics”, i.e., time intervals. Thetime duration of each pixel is measured by a plurality of such tics. Forexample, a pixel in the preferred embodiment can be measured as havingfrom 3 to about 14 tics, and up to 16 tics per pixel can be stored for ahigh degree of precision. A pixel counter 202 counts the pixels on eachscan line, and a line counter 204 counts the number of scan lines in theimage to be projected. The pixel and line counters 202, 204 areconnected to a profile memory that is advantageously embodied as thelook-up tables 132, 134, 136 of FIG. 7. A master line table 206 isconnected to a current line table 208 and its contents are reloadedevery frame.

The output of the current line table 208 is connected to an 8-bitaccumulator 210 having 4 upper bits for integer storage 212 and 4 upperbits for fractional storage 214, as described below. The output of theaccumulator is inverted in an inversion look-up table 216 whose outputis used for brightness compensation, as described below.

The duration of each pixel is not necessarily, and indeed is often not,an integer number of tics. Typically, the duration of a pixel is mostprecisely expressed as a number having a fractional remainder. Oneaspect of this invention is that the fractional remainder of a firstpixel is stored in the fractional storage 214 of the accumulator, and isthen taken into account for the next neighboring second pixel. Theduration of the neighboring second pixel is either rounded up or down asthe case may be. The contents of the accumulator after the duration ofthe second pixel has been determined are then taken into account for thethird and for all successive pixels on a scan line.

During a calibration mode, the profile memory is mapped with the timedurations of the pixels. There are various approaches. For example, thetime durations can be stored only for a single representative scan line,for example, the center scan line, in which case, the stored timedurations for the representative scan line are applied to all of theother scan lines; however, this leads to errors particularly at theupper and lower regions of the raster scan which are furthest from thecenter scan line. Alternatively, the time durations can be stored forall of the scan lines; however, this requires a multitude of storagelocations for the profile memory. Preferably, to minimize the memorystorage requirement, the time durations are stored for a single scanline, such as the center scan line, and then only the differences withthe adjacent scan lines are stored in succession for all the scan lines.

In further accordance with this invention, the stored time durationsfrom the accumulator 210 are inverted (the brightness is inverselyrelated to the time durations), and a brightness compensation signal isgenerated. This signal is then multiplied with the incoming video datato ensure that each pixel has the same brightness. The stored timedurations from the accumulator 210 are not rounded for this purposesince the brightness jumps more precipitously when rounded timedurations are used.

It will be understood that each of the elements described above, or twoor more together, also may find a useful application in other types ofconstructions differing from the types described above.

While the invention has been illustrated and described as embodied in anarrangement for and a method of projecting an image with pixel mapping,it is not intended to be limited to the details shown, since variousmodifications and structural changes may be made without departing inany way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.

1. An image projection arrangement for projecting a two-dimensionalimage on a projection surface, comprising: a) a laser assembly forgenerating a laser beam; b) a scanner for sweeping the laser beam as apattern of scan lines at a distance from the laser assembly on theprojection surface, the scanner including a scan mirror movable at aspeed that varies along each scan line, each scan line having a numberof pixels, the pixels having respective time durations proportional tothe variable speed of the scan mirror; c) a profile memory for storingthe time durations of the pixels; and d) a controller operativelyconnected to the laser assembly, the profile memory and the scanner, forcausing selected pixels along the scan lines to be illuminated for thetime durations stored in the profile memory, and rendered visible, bythe laser beam to produce the image.
 2. The image projection arrangementof claim 1, wherein the laser assembly includes a plurality of lasersfor respectively generating a plurality of laser beams of differentwavelengths, and an optical assembly for focusing and nearly collinearlyarranging the laser beams to form the laser beam as a composite beamwhich is directed to the scan mirror.
 3. The image projectionarrangement of claim 2, wherein the lasers include red and blue,semiconductor lasers for respectively generating red and blue laserbeams.
 4. The image projection arrangement of claim 3, wherein thelasers include a diode-pumped YAG laser and an optical frequency doublerfor producing a green laser beam.
 5. The image projection arrangement ofclaim 2, wherein the scan mirror is operative for sweeping the compositebeam along a first direction at a first scan rate and over a first scanangle, and wherein the scanner includes another oscillatable scan mirrorfor sweeping the composite beam along a second direction substantiallyperpendicular to the first direction, and at a second scan ratedifferent from the first scan rate, and at a second scan angle differentfrom the first scan angle.
 6. The image projection arrangement of claim5, wherein at least one of the scan mirrors is oscillated by an inertialdrive.
 7. The image projection arrangement of claim 1, wherein thecontroller includes means for energizing the laser assembly toilluminate the selected pixels for the time durations stored in theprofile memory, and for deenergizing the laser assembly tonon-illuminate pixels other than the selected pixels.
 8. The imageprojection arrangement of claim 1, and an accumulator for storinginteger and fractional time durations of the pixels.
 9. The imageprojection arrangement of claim 1, and an inversion table operativelyconnected to the accumulator for storing inverted time durations of thepixels, and for generating a brightness compensation signal.
 10. Animage projection arrangement for projecting a two-dimensional, colorimage on a projection surface, comprising: a) a support; b) a laserassembly including red, blue and green lasers on the support, forrespectively emitting a plurality of red, blue and green laser beams; c)an optical assembly on the support, for optically focusing andcollinearly arranging the laser beams to form a composite beam; d) ascanner on the support, for sweeping the composite beam in a pattern ofscan lines at a distance from the support on the projection surface, thescanner including a scan mirror movable at a speed that varies alongeach scan line, each scan line having a number of pixels, the pixelshaving respective time durations proportional to the variable speed ofthe scan mirror; e) a profile memory for storing the time durations ofthe pixels; and f) a controller operatively connected to the lasers, theprofile memory and the scanner, for causing selected pixels along thescan lines to be illuminated for the time durations stored in theprofile memory, and rendered visible, by the composite beam to producethe image, the controller being operative for selecting at least some ofthe laser beams to illuminate the selected pixels for the time durationsstored in the profile memory to produce the image with color.
 11. Theimage projection arrangement of claim 10, wherein the scan mirror isoperative for sweeping the composite beam along a first direction at afirst scan rate and over a first scan angle, and wherein the scannerincludes another oscillatable scan mirror for sweeping the compositebeam along a second direction substantially perpendicular to the firstdirection, and at a second scan rate different from the first scan rate,and at a second scan angle different from the first scan angle.
 12. Theimage projection arrangement of claim 10, and an accumulator for storinginteger and fractional time durations of the pixels.
 13. The imageprojection arrangement of claim 10, and an inversion table operativelyconnected to the accumulator for storing inverted time durations of thepixels, and for generating a brightness compensation signal.
 14. Animage projection arrangement for projecting a two-dimensional image on aprojection surface, comprising: a) laser means for generating a laserbeam; b) scanner means for sweeping the laser beam as a pattern of scanlines at a distance from the laser means on the projection surface, thescanner means including a scan mirror movable at a speed that variesalong each scan line, each scan line having a number of pixels, thepixels having respective time durations proportional to the variablespeed of the scan mirror; c) profile memory means for storing the timedurations of the pixels; and d) controller means operatively connectedto the laser means, the profile memory means and the scanner means, forcausing selected pixels along the scan lines to be illuminated for thetime durations stored in the profile memory means, and rendered visible,by the laser beam to produce the image.
 15. An image projection modulefor projecting a two-dimensional image on a projection surface,comprising: a) a support; b) a laser assembly on the support, forgenerating a laser beam; c) a scanner on the support, for sweeping thelaser beam as a pattern of scan lines at a distance from the support onthe projection surface, the scanner including a scan mirror movable at aspeed that varies along each scan line, each scan line having a numberof pixels, the pixels having respective time durations proportional tothe variable speed of the scan mirror; d) a profile memory for storingthe time durations of the pixels; and e) a controller operativelyconnected to the laser assembly, the profile memory and the scanner, forcausing selected pixels along the scan lines to be illuminated for thetime durations stored in the profile memory, and rendered visible, bythe laser beam to produce the image.
 16. A method of projecting atwo-dimensional image on a projection surface, comprising the steps of:a) generating a laser beam; b) sweeping the laser beam as a pattern ofscan lines on the projection surface by moving a scan mirror at a speedthat varies along each scan line, each scan line having a number ofpixels, the pixels having respective time durations proportional to thevariable speed of the scan mirror; c) storing the time durations of thepixels; and d) causing selected pixels along the scan lines to beilluminated for the stored time durations, and rendered visible, by thelaser beam to produce the image.
 17. The image projection method ofclaim 16, wherein the directing step is performed by generating aplurality of laser beams of different wavelengths, and the step offocusing and nearly collinearly arranging the laser beams to form thelaser beam as a composite beam which is directed to the scan mirror. 18.The image projection method of claim 16, and storing integer andfractional time durations of the pixels.
 19. The image projection methodof claim 16, and storing inverted time durations of the pixels, andgenerating a brightness compensation signal.